1. Field of the Invention
The invention relates to apparatus for permitting residential or business telephone subscribers to identify who is placing a telephone call to the subscriber.
2. Description of the Prior Art
U.S. Pat. No. 4,266,098 to Novak discloses a system capable of monitoring information contained in incoming telephone calls. The disclosed system automatically holds the incoming call and displays the identity of the caller. Ringing of the subscriber's telephone is initiated either at certain times and/or for certain callers. After the caller places a call to the subscriber, the call is interrupted and answered by an answering device. The answering device requests that the caller enter a code that has been previously provided to the caller. If the code matches a code within the answering device which code represents a telephone number that the subscriber had indicated a willingness from which to receive calls, the call will be rung through to the subscriber. This system has drawbacks. First, the caller would know that the subscriber has decided not to accept the call and not merely that the subscriber is not at home, which is the implication if the telephone at the subscriber location would ring without being answered. Second, the subscriber must enter and store in the system those codes either he will receive or that he will not receive instead of making the decision as to which calls he wants to accept when the call actually comes in. A third drawback is the requirement that the caller take some positive step in connection with completing the identification process instead of the procedure being carried out automatically, independent of any activity by the caller.
U.S. Pat. No. 4,242,539 to Hashimoto discloses a system in which the calling party's telephone number will be displayed at the subscriber location on a digital display device. The subscriber then has the option whether or not to answer the call after viewing the caller's telephone number. The telephone number of the calling party must be stored in the telephone exchange of the calling party and such number must be sequentially transmitted to the telephone exchange of the called party. Thus, the system depends upon modification and/or inclusion of additional equipment at each of the telephone exchanges. The disclosed system could not be put into operation without the inclusion of additional equipment at each subscriber location.
U.S. Pat. No. 3,787,626 to Subieta discloses a system for displaying the calling party's telephone number at the telephone set of the called party. Each of the calling locations must include a transmitter for transmitting a pulse train of audio frequency signals. The subscriber receives this signal and upon decoding the signal provides identification of the telephone number calling the subscriber. The subscriber then has the option of whether or not to answer the telephone. This system has the drawback of requiring both the callers and the subscriber to incorporate additional specifically designed equipment at each location.
U.S. Pat. No. 4,277,649 issued to Sheinbein describes a comprehensive and elaborate system for providing customized telephone services and for automatically screening calls to a call station wherein the nature of the screening is designated and controlled by the called station. According to this arrangement the called station having the screening service is provided with a memory located at a destination switching center which serves the station. The customer accesses the memory and enters in the memory the identity of all calling lines whose calls are to be screened. In addition, an indication is entered in the memory of the treatment to be given to calls incoming from these lines. When an incoming call arrives at the switching office containing the called station's memory, the control equipment ascertains if the called customer is provided with the special screening service feature. If this service feature is provided, a signal is sent to the originating switching office requesting the identity of the calling line. Using the calling line identity, the memory at the destination office is read to ascertain if the calling line is to be given the special treatment requested by the called party. The control equipment then disposes of the call according to the special treatment indication found in the memory location assigned to the calling line identity or sends a message to the originating office as to the disposition of the call. Among the special service treatments given calls from certain calling lines include selective call blocking, selective call waiting, selective call forwarding, distinctive ringing, special billing and many others. This arrangement requires considerable equipment, is relatively expensive and is primarily adapted to large installations.
U.S. Pat. Nos. 3,748,396 to Hestad et al and 4,017,689 to Richards et al describe PABX systems which provide for reception of both DID calls and regular calls to the PABX number group. Japanese Patent No. 154914 describes a switched access arrangement in which the identification of the calling number is supplied to an intended recipient while U.S. Pat. No. 4,071,699 to Jovic et al discloses delay of call completion pending identification of the calling line. Japanese Pat. No. 159111 discloses a system for recording the number and date of unanswered calls.
U.S. Pat. Nos. 4,289,931 to Baker; 3,727,003 to Paraskevakos; and 3,686,440 to Kroeger disclose systems similar to that previously described with reference to U.S. Pat. No. 3,787,626. Specifically, each of these patents discloses a system in which a signal is transmitted from the calling location which signal is received and decoded by the subscriber location for identifying the telephone number of the particular caller.